Method of preparing near-infrared spectrum filter media



tates Patent inc 2,992,938 Ratented July 18, 1961 2,992,938 METHOD OFPREPARING NEAR-INFRARED SPECTRUM FILTER MEDIA William J. McCarville andBernard S. Wildi, Dayton, Ohio, assignors to Monsanto Chemical Company,St. Louis, Mo., a corporation of Delaware No Drawing. Filed May 15','1958, Ser. No. 735,379 18 Claims. (Cl. 117-16) This invention relatesto a novel means of preparing light filter media which are useful forscreening out infrared radiation. More particularly this inventionrelates to the process of dusting finely divided infra-red barriercompositions onto the surface of a transparent or translucent plasticmaterial and burnishing the said compositions onto the surface of thesaid material.

Recent trends in design have provided increasingly large amounts oftransparent and translucent materials in homes, commercial buildings,factories, automobiles, marine craft, and the like. It is recognizedthat these materials also transmit infra-red radiation. Accordingly, theincreased exposure of the interior of architectural structures,vehicles, etc. to solar energy induces a relatively large temperaturerise therein especially in the summer months and in the southernlatitudes. Since the solar heat at sea level in mid-day is of the orderof about 300 B.t.u. per hour per square foot, it is apparent that theincreased exposure of the interior of objects to solar energy creates aproblem in maintaining comfortable conditions in said interiors. This isin part obtained by the use of air-conditioning equipment. It is alsopossible to substantially reduce the penetration of infra-red radiationthrough the transparent or translucent material by the use of variousinfra-red filter media which reflect or absorb the infra-red radiation,whereby the load on the airconditioning equipment can be materiallyreduced.

One class of organic compounds useful as infra-red filter media are thepolymethine dyes disclosed in US. Patent No. 2,813,802, which patent isincorporated herein by reference. The said polymethine dyes can bedescribed as bis(p-aminophenyl)vinylcarbonium compounds having thestructural formula:

/ l l l wherein n is an integer up to 3, and X is the anion of a strongacid. The polymethine dye compositions can be applied to transparent andtranslucent materials, generally in the form of sheets such as glass andvarious synthetic polymeric compositions, by treating with a solution ofthe dye as by spraying, flowing, pouring, brushing, etc. on the surfaceof the sheet. Also the dye can be applied as a fused liquid, or can bedusted onto the surface of the material as a comminuted solid and fusedin place by the application of heat thereto. However these methods ofapplication have inherent limitations which restrict the wideapplication of the polymethine dyes in infra-red filter media. Thus,many of the synthetic polymer compositions which may be desired as asupporting base for the dye film contain plasticizers, which are in partextracted during the solvent application of the dye solution, and maythen deleteriously affect the dye film, etc. Also the solvents for thepolymethine dyes tend to penetrate the synthetic polymer film basewhereby it is very difficult to obtain reflective filtering of infra-redradiation.

Applicatioin of the dye by fusion is limited to basematerials which haverelatively high melting points, since the melting point of the dyes arealso relatively high, and in addition it is difficult to get a uni-formcoating of the dye applied to the base material when it is spreadthereon as a comminuted solid and fused in place.

It is the principal object of the present invention to pro vide animproved method for the application of infra-red reflecting andabsorbing compositions to base materials. Another object of the instantinvention is to provide an improved method for the application ofpolymethine dyes to synthetic polymeric compositions. Other objects andadvantages of this invention will be apparent to those skilled in theart from the following disclosure.

It has now been found that the infra-red reflecting and absorbingcompositions can be applied to the base material as a finely comminutedsolid and then burnished by the application of a buffing means toprovide an improved infra-red filter media.

Films applied by the burnishing technique were found to be surprisinglyresistant to smearing or rubbing off and were much superior to similarfilms which were coated on the base material from a solvent composition.The films applied by the burnishing techinique withstood repeated hardrubbing with the fingers with little change in appearance. If thefingers were oily or moist, the reflection of the film was dulledslightly. After the film was applied it was found that it could berubbed with soft materials, e.g. cotton, and none of the infra-redreflecting and absorbing composition was transferred to the cotton andthe film was unaifected.

It will be understood that the infra-red barrier film applied by theburnishing technique also can be protected from abrasion by laminating aprotective transparent or translucent material over said film, e.g.glass or various light-transmitting polymeric compositions, or theinfrared barrier film can be protected by directly coating same with anabrasion-resistant polymeric composition.

For the best results the surface of the polymeric base material shouldbe clean, i.e. free from oil, and when the polymeric base material isrelatively thin it should be supported on a smooth, firm backing toavoid possible transfer of impressions of the backing to the infra-redreflecting and absorbing film. For the intermittent production ofinfra-red filter media by the burnishing technique a backing of clean,smooth, polished plate-glass or metal platen furnishes a suitablesupport, and for the continuous production of said film to a flexiblepolymeric base material the film preferably can be applied by burnishinga uniform application of the finely comminuted, solid, infra-red barriercomposition as it passes over one or more smooth rolls, e.g. a highlypolished metal roll. It is also possible to effect initial burnishing ofthe infrared barrier film onto the supporting plastic material andthereafter redust the surface and again burnish one or more times when aheavier barrier film is desired.

The particle size of the infra-red reflecting and absorbing compositionpreferably should be as fine as possible such that percent thereof couldpass a 400-mesh screen. Preferably the particle size of the solidmaterial should be at least of the order of about 2 to about 5 micronsor finer in order to provide a substantially uniform appearing film.

The bufiing means for burnishing the film can be any material which isnot abrasive to the polymeric base support for the film. Suitablebuffing materials are for example, cotton; wool; felt; fine-furredanimal pelts, e.g. rabbit and the like; soft pile fabrics prepared fromsynthetic polymers, e.g. nylon and the like; soft pads of syntheticpolymers, e.g. polyethylene; soft, pliant leather, e.g. chamois and thelike; etc. Only a light bufiing pressure need be applied, preferably notexceeding about 25 pounds per square inch. The lineal speed of thebuffing means preferably should not exceed about 50 feet per second, andmore preferably should be of the order of 7 about 2 to about 10 feet persecond. The burnishing time will vary somewhat depending on the pressureand lineal speed of the bufling means, but is of the order of a fractionof a second for mechanical burnishing up to about seconds for handburnishing, or longer.

The application of an infra-red reflecting and absorband the like.

films by the burnishing technique.

tially pure.

of the polymeric base composition.

illustrative examples:

media.

After exposing to solar radiation for a period of 100 days theappearance, and infra-red reflection and absorption were stillexcellent.

ing composition by the burnishing technique is suitable 5 Example 2 foruse on many polymer materials and is most suitable for the generallyharder surface polymeric compositions, An mfra'l'ed filter was Preparedthe same manner for example cellulose-based materials such as celluloseas Example 1, exeeptflhat a mll Sheet of cellulose acetate; polyvinylacetals such as polyvinyl butyral; polyacetate emPloYed 1h Place of thePolystyrene The vinyl aromatics such as Polystyrene; Polyvinyl.ehloride; 10 heptamethine perchloratefilm on the cellulose acetate basehad excellent reflectivity. The film appeared red- The polymethine dyecompositions of US. Patent No. e by reflected hght and blue bytrehemltted 2,813,802 are particularly suitable for application as hght-The filter exposed to Solar radlahoh for For best results it 150 days,after WhlCh time the appearance and infrahas been found that the dyecompositions Sought to be 15 red reflection and absorption of the filterwere still very coated on the plastic base material should be substaneIt was also found that the vlelhle trahsmlhahce other classes ofinflamed barrier materials vaned less than two percent after thisexposure time. which have also been found to be suitable are, for ex- EI 3 ample, the porphyrines such as copper phthalocyanine, xamp e zinctetraphenylporphine, zinc tetrabenzoporphine, tetra- 2Gbenzomonoazoporphine, tetraphenylporphine, octaphenyl- Solution of thedye h fP i1 1111 ethylene dlclilo porphyrazine, a,/8,',6-tetrakis(2-furyl)porphine, oc,fi,'y,bwas.coat.ed onto a s eet 0 Ce u056 Mfume p tetrakis(4-rnethoxyphenyl)porpl1ine etc.; and other typestlclzed wlth. methyl Phthalaie' After Y 5 Solar exof materials asexemplified hereinafter; and the like. The gg g ggg gi t s gg g g g gg gz zz 323 burnishing technique has also been found to be suitable 5 tothe same mgterial mechanican buriishin the for the application ofinorganic infra-red reflecting and d fil f 5 h f absorbing materials asexemplified hereinafter. ye was ound at t e galln m transmlsslon a terThe infra-red reflecting and absorbing material is genone years solarexposure was on y about 3 Percent erally applied in an amount such thatabout one pound Example 4 of the material is employed to provide a filmon the order of from about 15,000 to about 20,000 square feet Finelydivided rhenium oxide was dusted Onto a fil of polyvinyl butyralsupported on a smooth rigid sur- The instant invention is exemplified bythe following f Th a bufling pad of polyethylene film was ployed toburnish the rhenium oxide onto the polyvinyl Example 1 o butyral toprovide a reflecting film which adhered well Fi l powdered1,1Jltetrakis(p dimethy1aminophen to the plastic supportlng base and wasan eflective infrayl)trivinylcarbonium perchlorate was dusted onto thered filtersurface of a 10 mil sheet of biaxial oriented polystyreneNumerous other finely dlvlded Infra-fed bal'rlel' and bufled thereonwith a pad of fine absorbent cotton p s were buffed q sheets ofcellplqse c t e to to provide a film suitable for use as an infra-redfilter demonstrate the Wide utlllty 0f the bumlshlng teehmque The dyefilm Was then protected f o b ion for the preparationof infra-redfilters. The examples by coating with a polymethyl methacrylate lacquercomllsted 1n the followlng table were P p y dusting prising about 12.5parts by weight of polymethyl meththe specific compound onto the surfaceof a clean sheet acrylate, 44.5 parts by weight of perchlorethylene andof cellulose acetate and hand-buffing for a few seconds 4o 43.0 parts byweight of ahphatic petroleum naphtha. w1thapad of fine absorbent cotton.

Example Compound Color by Color by Quality of transmission reflectionreflectance 1,1,151,5tetrakls(p-dimethylaminophenyl)divinylcarboniumphos- Blue Copper Excellent.

a e. 1,1 ?5,5-tetrakis (p-dlmethylarnlnophenyl)divinylcarbonlum phthal-Do.

oeyantne sulfonate. 1,1,3-tris (p-dimethylaminophenyl)vlnylcarboniumperchlorate- Do. 1,3-bis 2(4,6-diphenylthiopyrylium)vinylcarboniumperchlorate- Very good. Copper phthalocyanine Excellent. Zinctetrabenzoporphinc Very good. Zinc tetraphenylporphille Excellent.Tetraphenylporphine- D0. Tctrabenzoporphine Good. Tetrabenzomonoazoporphe Very good. Copper tetrabenzomonoazopornnine Excellent.Tetrabenzodiazoporphine Do. Copper tetrabenzotriazoporphinc Do. m6,fi-Tetrakis(4-methyl)-p0rphine. Very good a,fl,,5-Tetrakis(a-thienyD-porphine Do. a,fi,'y,6-Tetrakis(4-l1ydr0xyphenyl)porphine D0 01,13, ,6-Tetrakis(4-meth0xyphenyl)p0rpExcellent a,B,'y,6 TetIakis(2,4dichl0rophenyl)pornninc Good. (1,5,,6-Tetrakis(l-naphthyl)-porphine Very good Zinc a,B,,-tetrakis(4-pyridyl)porphine Do. Tetrahydroporphyrine Excellent.Octaphenylporphyrmino Very good. Copper Z-phenacylpyrldine- Good. Dithone Do. 6,14-dinaphthanaphtho-[1,8a,8,2a,b,c,1,8a,8,7-j,k,l]coroneneExcellent. Rhodamine B Do. 0min GOOd. Cyanine green- Excellent.Bromocresol purple Good. Quinalizariu- Do. Chloranil-hydro qulnone Do.Chlorantine 4G1: Excellent.

Luxol fast blue Good.

For glazing materials the infra-red filter ideally should transmit thevisible light with little reflection or absorption and should efl'ect arelatively large reduction in the transmission of infra-red radiation,principally by reflection. In practice the infra-red barrier film alsofunctions by absorption, but it Will be apparent that the reflectivefilm is more efficient. Accordingly, the burnishing technique is a veryuseful improvement in that it provides a means of obtaining films havinga high order of reflection in contradistinction to many films preparedby solvent application.

The infra-red filter media prepared by the burnishing technique areuseful as commercial heat screens and find particular use inarchitectural applications such as in dustrial, commercial, andresidential glazing. These infra-red filter media are also useful forautomotive, marine craft and aircraft glazing; for sun glasses, weldersgoggles, and the like.

We claim:

1. A method of preparing an infra-red filter media comprising dusting acoating of a finely divided minus 400-mesh, solid, infra-red barriercomposition, selected from the group consisting of organic dyes,organometallic dyes, and rhenium oxide, onto the surface of a visiblelight transmitting plastic material and burnishing the infra-red barriercomposition onto the surface of said material and the final filterproduct transmits visible light.

2. The method of claim 1, wherein the lineal speed of the buffer doesnot exceed about 50 feet per second, and the buifing pressure does notexceed about 25 pounds per square inch.

3. The method of claim 2, wherein the particle size does not exceed ofthe order of about 5 microns and the lineal speed of the buffer is fromabout 2 to about feet per second.

4. The method of claim 1, wherein the infra-red barrier composition is abis(p-aminophenyl) vinylcarbonium compound of the class wherein n is aninteger from 0 to 3, inclusive, and X- is the anion of a strong acid.

5. The method of claim 4, wherein the infra-red barrier composition is1,1,7,7-tetrakis(p-dimethylaminophenyl) trivinylcarbonium perchlorate.

6. The method of claim 4, wherein the infra-red barrier composition is1,1,5,5-tetrakis(p-dimethylaminophenyl) divinylcarbonium perchlorate.

7. The method of claim 4, wherein the infra-red barrier composition is1,7-bis[4-(N,N-dimethylamino)- phenyl] -1,7-bis(phenyl)trivinylcarbonium perchlorate.

8. The method of claim 4, wherein the infra-red barrier composition is1,S-bis[4-(N,N-dimethylamino)phenyl]-l,5-bis (phenyl)divinylcarboniumperchlorate.

9. The method of claim 4, wherein the infra-red barrier composition is1,5-bis[4-(N,N-dimethylamino)phenyl]-1,5-bis(phenyl)divinylcarboniump-toluenesulfonate.

' 10. The method of claim 4, wherein the plastic material is celluloseacetate.

11. The method of claim 4, rial is polystyrene.

12. The method of claim 4, rial is polyvinyl butyral.

13. The method of claim 4,

wherein the plastic matewherein the plastic matewherein the plasticmaterial is polyvinyl chloride.

References Cited in the file of this patent UNITED STATES PATENTS2,281,100 Land Apr. 28, 1942 2,813,802 Ingle et a1 Nov. 19, 19572,817,603 Louis Dec. 24, 1957

1. A METHOD OF A PREPARING AN INFRA-RED FILTER MEDIA COMPRISING DUSTINGA COATING OF A FINELY DIVIDED MINUS 400-MESH, SOLID, INFRA-RED BARRIERCOMPOSITION, SELECTED FROM THE GROUP CONSISTING OF ORGANIC DYES,ORGANOMETALLIC DYES, AND RHENIUM OXIDE, ONTO THE SURFACE OF A VISIBLELIGHT TRANSMITTING PLASTIC MATERIAL AND BURNISHING THE INFRA-RED BARRIERCOMPOSITION ONTO THE SURFACE OF SAID MATERIAL AND THE FINAL FILTERPRODUCT TRANSMITS VISIBLE LIGHT.